If cats are left with fleas for too long, it can cause serious health problems. Fleas can spread diseases such as feline typhus and anemia, which can be fatal in extreme cases. Fleas also cause discomfort and itching, which if ignored too long can lead to a skin infection or fur loss. In addition, fleas feed on the blood of cats and when they are not treated it can cause anemia due to depletion of red blood cells. It’s important to take preventative measures to avoid infestations of fleas if possible, such as never leaving pets outside unsupervised and regularly grooming them with a flea comb. If you suspect your cat has a flea problem, it’s best to contact your veterinarian immediately to identify and treat the source of infestation before more serious illness arises from leaving them untreated too long.